Various technologies have been developed to accurately position a tool on a mobile machine. These technologies are useful in applications such as construction, mining, and other industries, in which it may be necessary to achieve very tight tolerances. On a construction site, for example, it may be necessary to add or remove earth from a given location to accurately provide a specified design elevation, which may be different from the initial surface elevation. A machine such as an excavator, grader, or bulldozer equipped with a shovel, bucket, blade, or other appropriate tool is typically used. Hence, the tool must be positioned accurately to achieve the required tolerances.
Some machine control systems rely upon a stationary rotating laser or a robotic total station to assist in accurately positioning the tool. However, such systems are limited to operation with only one machine at a time. In addition, laser based systems are limited by line of sight. Thus, obstructions in the work area, such as other machines, may impair operation of the system. Further, many such systems are effective only when used on very level terrain. Hence, what is needed is a system for accurately positioning a tool on a mobile machine, which overcomes these and other disadvantages.